The invention relates to a signal converter, in one embodiment an analog-digital converter, and to a method for operating a signal converter.
Conventional microcontroller or microprocessor systems include one or a plurality of (central) control or processing units (Central Processing Units (CPUs), or CPU “cores”) that are connected with one or a plurality of memories, e.g., a program and a data memory means (“program memory” and “data memory”). The memories may be provided on one and the same chip as the corresponding microcontroller or microprocessor (so-called “embedded” microcontroller or microprocessor system), or may alternatively also be provided separately therefrom. The “program memory” includes in particular the sequence of instructions to be processed by the CPU core(s), i.e. the program (and possibly additionally corresponding data constants to be used by the CPU core(s)). In the “data memory”, the variables—that are possibly to be modified in particular by the CPU core(s) during the execution of the program—may be stored.
Conventional microcontroller or microprocessor systems—e.g., systems that are used in the automotive field—frequently also include one or a plurality of signal converters, in particular analog-digital converters.
By using an analog-digital converter, an analog input signal, e.g., a corresponding measurement voltage, may be converted to a digital numerical value that is “understandable” for the corresponding microcontroller or microprocessor processing unit.
Analog-digital converters may operate in accordance with a plurality of different converting methods, e.g., the parallel method, the weighing method, or the counting method, etc. (or also mixed forms thereof).
In the case of the parallel method, the input signal or the input voltage, respectively, is, by using corresponding comparators, simultaneously compared with n different reference voltages, and it is determined between which two reference voltages the input voltage ranges. This way, the digital numerical value or the corresponding dual number, respectively, pertaining to the input signal may be determined in one single step or process. The relatively high switching effort is, however, of disadvantage since a relatively great number of comparators are needed.
In the case of the weighing method, other than with the parallel method, the digital numerical value pertaining to the input signal is not determined in one single step, but in several processes, wherein only one respective position of the corresponding dual number is determined per step. In so doing, the respectively highest dual number position is initially started with, and it is determined whether the input voltage is greater or smaller than the reference voltage assigned to the highest dual number position (which may in particular e.g., correspond to half the value of the corresponding maximum voltage). If the input voltage is smaller, the highest position is set to “0”, otherwise to “1”, and the reference voltage assigned to the highest dual number position is subtracted from the input voltage. Next, it is determined whether the input voltage or the remaining voltage obtained by the above-mentioned subtraction, respectively, is greater or smaller than the reference voltage assigned to the next-highest dual number position (which may in particular e.g., correspond to a quarter of the maximum voltage). If it is smaller, the next-highest position is set to “0”, otherwise to “1”, etc. In the case of the weighing method, a number of comparison steps and reference voltages corresponding to the number of positions of the dual number is thus required.
In the case of the counting method it is determined how often the reference voltage assigned to the lowest position of the dual number has to be added to obtain the input voltage. The number of processes necessary for determining the digital number value pertaining to the input voltage corresponds to the respective digital number value, i.e. the counting method is relatively little expensive, but relatively slow.
Conventional analog-digital converters may include several, different input channels via which the input voltages to be converted are supplied to the corresponding analog-digital converter.
By using an analog multiplexer, one respective of the input channels can be selected, and the signal present at this input channel can be supplied to the actual converter.
For each input channel, a register that is specifically assigned thereto may be provided, by which additional information that is applicable for the respective input channel is provided for the converter.
The additional information stored in the above-mentioned registers may, for instance, be indications concerning the “sample time”—depending, for instance, on the impedance of the source connected to the input channel—to be used for the respective input channel, i.e. the time that has to be waited until the actual voltage measurement can be performed.
Alternatively or additionally, information about the reference voltage to be used for the respective input channel may, for instance, also be stored in the above-mentioned registers, and/or a plurality of further parameters concerning the respective input channel.
The fact that an own register is provided for each input channel results—in particular with a relatively high number of input channels—in a relatively high space requirement.
With alternative prior art solutions, one single register is used for all input channels, i.e. respectively identical additional information for all input channels.
This results in a relatively low flexibility of the corresponding analog-digital converter.
For these and other reasons, there is a need for the present invention.